Yazama Futoshi
Laboratory of Cell Biology and Morphology, Department of Life Science, Prefectural University of Hiroshima, Hiroshima, Japan.
J Reprod Dev. 2008 Oct;54(5):299-305. doi: 10.1262/jrd.19169. Epub 2008 Jun 10.
Tight junctions occur between the lateral processes of neighboring Sertoli cells that divide the seminiferous epithelium into two compartments: basal and adluminal compartments. These tight junctions constitute the blood-testis barrier (BTB). The established theory that the BTB must open when spermatocytes translocate from the basal compartment to the adluminal compartment is marked by one contradiction, that is, normal spermatogenesis occurs in the testis because the BTB is expected to constantly seclude the adluminal compartment from the basal compartment in order to protect haploid germ cells from the autoimmune system. Subsequently, another concept was proposed in which two BTBs divide the seminiferous epithelium into three compartments: basal, intermediate and adluminal compartments. It has been suggested that the transition from the basal region to the adluminal region without the BTB open occurs through the agency of a short-lived intermediate compartment embodying some primary spermatocytes. In contrast, the results of recent findings in the molecular architecture of the BTB suggest that the BTB in the seminiferous epithelium must "open". In this paper, I re-examine the BTBs of boar and experimental cryptorchid mouse testes by transmission electron microscope (TEM). TEM analysis showed that an atypical basal compartment existed in the thin seminiferous epithelium of 14-day post-cryptorchid mice testes. In developmental boar testes, ectoplasmic specialization (ES) of the seminiferous epithelium showed dynamic behavior. The intermediate compartment was clearly observed between the basal and adluminal compartments of the mature boar seminiferous epithelium. ESs were observed between Sertoli cells and spermatids at all developmental stages, including early, late and mature. Furthermore, ESs were situated on the apical surface of the seminiferous epithelium. From these results, I propose that the BTB is continually maintained during spermatogenesis and suggest a model of ES circulation in the seminiferous epithelium.
紧密连接存在于相邻支持细胞的侧面突起之间，这些突起将生精上皮分为两个区域：基底区域和管腔区域。这些紧密连接构成了血睾屏障（BTB）。既定理论认为，当精母细胞从基底区域向管腔区域迁移时，BTB必须打开，但这一理论存在一个矛盾之处，即正常的精子发生在睾丸中，因为BTB预计会持续将管腔区域与基底区域隔离开来，以保护单倍体生殖细胞免受自身免疫系统的攻击。随后，又提出了另一种概念，即两个BTB将生精上皮分为三个区域：基底区域、中间区域和管腔区域。有人认为，在BTB未打开的情况下，从基底区域到管腔区域的转变是通过一个包含一些初级精母细胞的短暂中间区域实现的。相比之下，最近关于BTB分子结构的研究结果表明，生精上皮中的BTB必须“打开”。在本文中，我通过透射电子显微镜（TEM）重新检查了公猪和实验性隐睾小鼠睾丸的BTB。TEM分析表明，在隐睾小鼠睾丸术后14天的薄生精上皮中存在一个非典型的基底区域。在发育中的公猪睾丸中，生精上皮的外质特化（ES）表现出动态行为。在成熟公猪生精上皮的基底区域和管腔区域之间清晰地观察到了中间区域。在所有发育阶段，包括早期、晚期和成熟阶段，在支持细胞和精子细胞之间都观察到了ES。此外，ES位于生精上皮的顶端表面。基于这些结果，我提出在精子发生过程中BTB是持续维持的，并提出了生精上皮中ES循环的模型。
